Production of amines

ABSTRACT

1. IN THE LOW TEMPERATURE HYDROGENATION OF NITRATED HYDROCARBONS TO FORM CORRESPONDING AMINES HAVING FROM 6 TO 25 CARBON ATOMS ALONG WITH BY-PRODUCT WATER WHEREIN SAID HYDROCARBON AND HYDROGEN ARE CONTACTED WITH A CATALYST COMPOSED OF A GROUP VIIB OR VIII METAL ON CARBON UNDER HYDROGENATION CONDITIONS INCLUDING RECTION TEMPERATURES OF FROM 100 TO 450*F., THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID HYDROGENATION IN THE PRESENCE OF SAID CATALYST STABILIZED BY HEATING SAID CATALYST FOR AT LEAST ONE HOUR AT A TEMPERATURE OF BETWEEN 500 AND 1200*F. IN THE PRESENCE OF A NON-OXIDIZING GAS SELECTED FROM THE GROUP CONSISTING OF NITROGEN, MEHTANE, ARGON, HELIUM, NEON, ETHANE, PROPANE, HYDROGEN AND MIXTURES OF HYDROGEN AND LIGHT PARAFFINS UNDER A PRESSURE OF 0 TO 1,000 P.S.I.G.

United States Patent f PRODUCTION OF AMINES Robert M. Suggitt,Wappingers Falls, N.Y., assignor to Texaco Inc., New York, N.Y. NoDrawing. Original application Nov. 6, 1970, Ser. No. 87,599, now PatentNo. 3,736,265. Divided and this application July 24, 1972, Ser. No.274,552

Int. Cl. C07c 85/10 US. Cl. 260-583 M 12 Claims ABSTRACT OF THEDISCLOSURE A Group VIIB or VIII metal on carbon catalyst is stabilizedby heating the catalyst at a temperature of from 500 to 1200" F. in anon-oxidizing atmosphere. The heat treated composition is provided withstabilized activity and improved crush strength in low temperaturecatalyticreactions involving the reduction of nitrated or oxygenatedhydrocarbon to amines and alcohols where copious amounts of by-productwater is formed and is particularly suited for utilization as ahydrogenation catalyst such as in the selective conversion ofmono-nitroparaffins to secondary alkyl primary amines.

BACKGROUND OF THE INVENTION This is a division of application Ser. No.87,599, filed Nov. 6, 1970. Now US. Pat. No. 3,736,265.

This invention relates to improved catalytic compositions. Inparticular, this invention relates to improved Group VIIB and VH1 metalon carbon catalysts possessing stabilized activity and improved crushstrength.

Group VIIB and VIII metals of the Periodic Chart have been employed ascatalyst components and are of interest in a plurality of processesincluding hydrogenation and various methods for manufacturing the samehave heretofore been suggested. Customarily such hydrogenation catalystsare heterogeneous formulations in which the catalytically active GroupVIIB or VIII metal forms a minor component of the catalyst and isdistributed on a variety of supports exemplary of which are carbon,alumina, silica, aluminosilicates and the like. The support as acomponent of the heterogeneous catalyst may in many instances initiallyprovide acceptable activity and mechanical strength. However, inasmuchas water is a by-product of many hydrogenation reactions involvingorganic compounds, the heterogeneous catalysts are easily softenedleading to catalyst disintegration or poisoned at relatively lowprocessing temperatures such that activity progressively declinesthereby making the presently available catalysts unattractive forcommercial size operations.

It is therefore an object of this invention to provide a catalyticcomposition possessing extended catalytic life.

Another object of this invention is to provide a catalytic compositionpossessing stabilized activity and high crush strength.

Yet another object of this invention is to provide a method forpreparing a catalyst having long catalytic life wherein the catalyst issubjected to a stabilization step which does not adversely affect thecatalytic activity.

A further object of this invention is to provide a hydrogenation processundertaken in the presence of a catalyst possessing stabilized activityand high crush strength.

Other objects and advantages will become apparent from a reading of thefollowing detailed description of the invention.

SUMMARY OF THE INVENTION Broadly, this invention contemplates a methodfor stabilizing a Group VIIB or VIII metal on carbon catalyst whichcomprises heating the catalyst for at least one hour at a temperature offrom 500 to 1200 F. in the presence of a non-oxidizing gas. In a highlypreferred embodiment, the Group VIIB or VIII metal on carbon catalyst isheated at a temperature of from 700 to 1100 F. for a period of 2 to 8hours in the presence of hydrogen.

In another embodiment, this invention contemplates the low temperaturehydrogenation of nitrated or oxygenated C to C hydrocarbons to thecorresponding amine and alcohol wherein the hydrocarbon and hydrogen arecontacted with a catalyst composed of a Group VIIB or VIII metal oncarbon heat treated for at least one hour at a. temperature of from 500to 1200" F. in the presence of a non-oxidizing gas.

In accordance with this invention, the stabilized catalysts comprisefrom about 0.1 to 10.0 weight percent of a Group VIIB or VIII metal,preferably 015 to 2.0 weight percent, supported on a base of activatedcarbon. Exemplary of the metals contemplated herein are rhenium,platinum, palladium, rhodium and ruthenium. Combinations of metals arealso contemplated such as platinum-rhenium. Particularly preferredmetals are palladium, platinum and rhenium.

Activated carbons as a component of the heterogeneous catalyst representa class of known materials that are customarily prepared from coal,petroleum coke, animal or vegetable material. The raw material is firstcarbonized by heating at temperatures of from about 600 to 1200 F. in anon-oxidizing atmosphere and thereafter activated in a flow of steamcontaining a minor amount of air or superheated steam at temperatures of1200 to 1700 F. In addition to increasing the pore volume and surfacearea, this activating treatment introduces oxygen to the carbon surfacewhich is held in various forms generally described as surface oxides.Such partially oxidized carbon surfaces are hydrophilic and beneficiallypermit the wetting of the activated carbon with aqueous impregnatingsolutions of Group VIIB or VIII metal.

In a specific embodiment of this invention, it is preferred that theactivated carbons possess an ash con tent of below 5 weight percent andparticularly below 2 weight percent. Activated carbons having ashcontents below 5 weight percent also represent a class of commerciallyavailable materials known as water treating agents and absorbents forlow molecular weight hydrocarbon gases. The ash content of activatedcarbon is determined by burning the carbon at glowing red heat leavingan inorganic oxide residue composed of silicon, aluminum, iron, calciumand magnesium and traces of titanium, sodium and sometimes nickel andvanadium. As is also known, the activated carbon can be acid treatedwith for example hydrochloric acid to provide ash contents of below 2%where the predominant inorganic oxide residue is silica. In general, theactivated carbons described above and employed as catalyst supportsherein are conveniently provided in pelleted or extruded form. Theactivated car bon forming the support for the heterogeneous catalyststabilized by the method of this invention is one having a. high surfacearea, typically from about 800 to 1400 square meters per gram.

To prepare the heterogeneous catalysts stabilized herein, the activatedcarbon is impregnated with an aqueous solution of the salt.Illustratively, a metal, such as platinum, is provided by contacting theactivated carbon with an aqueous solution of chloroplatinic acid andethylene diamine. In the instance where a palladium catalyst iscontemplated, aqueous solution of palladium chloride or palladiumnitrate are introduced to the activated carbon. After thoroughly mixingthe impregnating solution and carbon, drying is undertaken attemperatures of 200 to 250 F., and a catalytically active platinum orpalladium on carbon composition is recovered. In a similar manner otherGroup VIII metals such as rhodium or ruthenium and Group VIIB metalssuch as rhenium are introduced thereby providing the heterogeneouscatalysts subsequently stabilized by this invention.

The composite prepared above while initially possessing high catalyticactivity and crush strength when employed as a hydrogenation catalyst,progressively loses activity within short periods of time on beingexposed to reaction by-product water. It has now been found that heattreating the catalyst for periods of at least one hour and up to 24hours and preferably from 2 to 8 hours at temperatures ranging from 500to 1200 F. preferably between the 700 and 1100 F., in a nonoxidizingatmosphere provides the catalyst with stabilized activity and prolongedcrush strength. It is believed that the treatment reduces and removessurface oxides and renders the catalyst more hydrophobic. A plurality ofnon-oxidizing environments can be used including such gases as nitrogen,methane, argon, helium, neon, ethane and propane. In a highly preferredembodiment, the nonoxidizing atmosphere is an environment of hydrogen ormixtures of hydrogen and light hydrocarbons, the latter atmosphere beingavailable, for example, from a catalytic reforming unit off-gas. Thepreferred environment, namely a reducing atmosphere of hydrogen, hasbeen found to give rise to superior catalysts possessing prolonged andincreased catalytic activity during use in the course of hydrogenationreactions producing copious amounts of by-product water and particularlywhen the heat treatment is conducted at temperatures of from 700 to 1100F. In general, the heat treatment in a non-oxidizing atmosphere isconducted under environment pressures of from O to 1000 p.s.i.g. andpreferably 300 to 700 p.s.i.g. Conversely, oxidizing conditions such asthe presence of air or oxygen during the heat treatment leads to rapidsoftening of the catalyst prior to use and deactivation when employed inreactions where water is a by-product.

One method of stabilizing the catalyst is to pass a gaseous stream ofnon-oxidizing gas over and through a bed of the catalyst at thetemperatures and pressures recited above where the gas is introduced atthe rate of at least 50 standard cubic feet per hour per square foot ofreactor cross section over a period of at least one hour and preferably2 to 8 hours.

The stabilized Group VIIB or VIII metal on carbon catalysts areparticularly suited for employment as hydrogenation catalysts in lowtemperature conversion reactions conducted at 100 to 450 F. underhydrogen pressures of from 10 to- 300 atmospheres and liquid hourlyspace velocities of from 0.2 to 20 involving the reduction of nitratedor oxygenated C to C paraflinic or olefinic hydrocarbons to amines andalcohols where water is a by-product of the reaction. Illustrative ofthe hydrogenation reactions employing the stabilized catalysts includethe reduction of mono-nitroparafiins to secondary alkyl primary aminesand secondary alkyl secondary amines, oximes to amines, nitroolefins toamines, fatty acids to alcohols and nitroketones, nitroalcohols andnitronitrates to amino alcohols.

In one preferred low temperature reaction, the stabilized catalyst isemployed in a process for producing secondary alkyl primary amines byreacting a mono-nitroparaflin having from 6 to 25 carbon atoms withhydrogen. Mono-nitroparaffins contemplated in such a process constitutesecondary nitro-n-parafiins in which the nitro group is randomlypositioned along the carbon chain on other than a terminal atom.Illustrative mono-nitroparaflins include 2 or 3-nitrohexane, 2,3 or4-nitroheptane, 2,3 or 4-nitrooctane, 2,3,4 or S-nitrodecane, 2,3,4,5 or6-nitroundecane, 2,3,4,5 or 6-nitrododecane, 2,3,4,5,6 or 7-nitrotridecane 2,3,4,5,6 or 7-nitrotetradecane, 2,3,4,5,6,7, 8 or9-nitrooctadecane and mixtures thereof, for example, mixtures of C -Cnitroparalfins. The applicable mono-nitroparafiins are prepared bycontacting a 'C C paraffin hydrocarbon, preferably a straight chainhydrocarbon, in a liquid phase with a vaporous nitrating agent such asnitrogen dioxide or nitric acid at a temperature ranging from about 250to 500 F. at from 1 to 20 atmospheres.

The illustrative nitration reaction briefly outlined above whetherperformed batchwise or in a continuous manner is generally permitted toproceed until about 5 to 50% of the paraffin has been converted yieldinga crude nitrated product of about 5 to 45% of mono-nitroparaffin and to50% unreacted paraffin along with lesser amounts of C -C ketone,alcohol, carboxylic acid and polyfunctionals. The mono-nitroparaffins soprepared may if desired to separated and recovered from the crudeproduct as by distillation and subsequently hydrogenated to thecorresponding amine, the reaction conveniently undertaken in thepresence of a C C paraflin hydrocarbon diluent. Alternatively, crudematerial may be hydrogenated directly wherein the unreacted paraffinconstitutes the reaction medium. The crude nitrated product may also becaustic washed with, for example, sodium bicarbonate, ammoniumhydroxide, sodium hydroxide or potassium hydroxide to remove acidby-products following nitration and prior to hydrogenation. Where thenitroparaffin feedstock is provided substantially free of acidby-products or contaminants neutralization may be omitted.

In one embodiment, the nitroparafiins are reduced to secondary alkylprimary amines in the presence of the stabilized palladium-carboncatalyst at temperatures of from about to 450 F. and preferably between200 and 400 F. under hydrogen pressures ranging from about 10 to 300atmospheres and preferably 20 to 40 atmospheres. The reaction isexothermic in nature and temperatures exceeding 450 F. are deleteriousto the formation of primary amines. At temperatures above 450 F.formation of secondary amine is substantially increased. Where secondaryamines are desired alone or in admixture with the primary amine,stabilized platinum or rhenium on carbon catalysts beneficially directselectivity in such a direction. The proportions of nitroparafiin tocatalyst are not critical and the optimum proportions are readilydetermined by experiment. In general, the higher the ratio of catalystto nitrocompound the more rapid the reaction.

The process described above is applicable to batchwise or continuousoperations. Suitable reactors may be charged and pressurized, agitationpreferably being provided and the reaction allowed to proceed andcontrolled by hydrogen pressure. Alternatively, continuous operationsmay be employed where the nitroparafiin is permitted to pass through andover the catalyst in the presence of hydrogen and under conditions oftemperature and pressure mentioned above and space velocities rangingfrom about 0.2 to 20 v./v./hr.

Conventional recovery procedures may be employed in recovering the amineas by distilling the crude reaction product by stepwise fractionation.Alternatively, the amine may first be converted and recovered as anamine salt by reaction with an inorganic acid followed by furthertreatment of the amine salt with alkali and thereafter recovering theprimary amine by distillation. Amines produced according to this processmay 'be employed as mold release agents, emulsion freeze-thawstabilizers, pigment dispersing agents, polyurethan catalysts andanti-caking anti-dusting agents. Their uses are also indicated ascorrosion inhibitors, deleterious bacteria control agents, sludgedispersants and as detergents and de-icers in gasolines.

The illustrative hydrogenation reactions outlined above undertaken attemperatures of from about 100 to 450 F. under hydrogen pressures offrom 10 to 300 atmospheres and liquid hourly space velocities of fromabout 0.2 to 20.0 after a period of prolonged on stream time may causethe catalyst to become partially deactivated. Regeneration of thecatalyst is easily undertaken by again contacting the catalyst with astream of non-oxidizing gas, preferably hydrogen, under the conditionsof temperature and time recited for initial stabilization such that thecatalyst activity is restored. Initial heat treatment and subsequentregeneration may be carried out in situ within the conversion reactor.

In order to more fully illustrate the nature of this invention andmanner of practicing the same, the following examples are presented. Inthese examples, the best mode contemplated for carrying out theinvention is set forth.

EXAMPLE I A composite of palladium on activated carbon was prepared bydissolving grams of palladium chloride in 100 cc. of water, 100 cc. ofconcentrated ammonium hydroxide and 400 cc. of methyl alcohol and addingthe resulting solution to 594 grams of commercially available extrudedactivated carbon pellets at about 32 F. and gently stirring the mixturefor one hour. The solids were thereafter recovered by filtration anddried at 135 F. for 16 hours and subsequently at 220 F. for 6 hours in astream of nitrogen. A catalyst composed of 574 grams of 0.97 weightpercent palladium on activated carbon was recovered.

A 54 gram sample of the above catalyst was heat treated in a 1 inchdiameter reactor at 450 F. for 4 hours in a stream of hydrogen flowingat the rate of 1-2 cubic feet per hour at 600 p.s.i.g. and labelledCatalyst A.

Two additional 54 gram samples of catalyst were heated to 1050 F. for 4hours in a stream of hydrogen flowing at the rate of 1-2 cubic feet perhour at 600 p.s.i.g. and labelled Catalysts B and C.

A C -C feedstock composed of 14.6 weight percent nitrated n-parafi'ln,82.1 weight percent n-paraffin, 0.4 weight percent ketone and 2.9 weightpercent difunctional paraflin was introduced at the rate of 100 gramsper hour into a hydrogenation reactor containing 54 grams of Catalyst Aand into another hydrogenation reactor containing 54 grams of CatalystB, each reactor maintained at a temperature of 275 F. and 600 p.s.i.g.of hydrogen. Product analysis after 60 hours on stream employingCatalyst A showed that this catalyst had lost 11% of its activitybetween the 12th and 48th hour on stream. Under the same operatingconditions Catalyst B demonstrated its stabilized activity by remainingwithin 4% of its activity over a period of 12 to 48 hours in convertingthe nitroparaffin to primary amine.

The C -C nitrated n-parafiin feedstock was introduced into ahydrogenation reactor containing 54 grams of Catalyst C maintained at atemperature of 275 F. and a hydrogen pressure of 600 p.s.i.g. at ahydrogen flow rate of 1.5 to 2.0 cubic feet per hour where the feed wasintroduced at the rate of 130 grams per hour. After a period of 80 hourson stream Catalyst C showed no deactivation.

EXAMPLE II A composite of palladium on activated carbon was prepared bydissolving 6.7 grams of palladium chloride in 70 cc. of water to whichwas added 100 cc. of concentrated ammonium hydroxide and 240 cc. ofmethyl alcohol. This solution was added to 490 grams of commerciallyavailable activated carbon inch pellets having an ash content of 3.51%.The mixture was gently stirred for one hour at 32 F. and the solids werethereafter recovered by filtration and dried at 220 F. for 4 hours in astream of nitrogen. The catalyst composed of 0.92 weight percentpalladium basis chemical analysis on activated carbon was recovered andlabelled Catalyst D. The crush strength of this catalyst was 14.3 poundsand was determined by measuring the force required to crack the catalystpellet between two parallel plates as force is applied slowly.

A 57 gram sample of Catalyst D was heat treated in a one inch diameterreactor at 500 F. for 2 hours in a stream of hydrogen flowing at therate of IV: to 2 cubic feet per hour at 600 p.s.i.g. and labelledCatalyst E.

Another 58 gram sample of Catalyst D was heated at 950 F. for 2 hours ina stream of hydrogen flowing at the rate of 1 to 2 cubic feet per hourat 600 p.s.i.g. and labelled Catalyst F.

A C -C feedstock as in Example I was introduced at the rate of cc. perhour into a hydrogenation reactor containing 60 grams of Catalyst D andinto another reactor containing 57 grams of Catalyst E each reactormaintained at a temperature of 275 F. and 600 p.s.i.g. of hydrogen.Product analysis of the feed contacted with Catalyst D showed that thiscatalyst rapidly deactivated with time on stream and lost 11% of itsactivity between the 8th and 28th hour on stream. Product analysis ofthe feed contacted with Catalyst E showed that this catalyst did notlose activity after 40 hours on stream.

Catalyst F, 58 grams, was similarly evaluated with a feedstock wasintroduced at the rate of 125 cc. per hour and 275 F. Catalyst Fevidenced no deactivation with time on stream and analysis of a productdemonstrated the catalysts high selectivity in that 9.7 milligrams of NHas primary amine per gram of product was produced along with nosignificant amount of secondary amine. When the processing conditionswith Catalyst F were changed to 225 F. and 60 cc./hr. liquid flow, highconversion was again obtained with no deactivation with time on stream.The crush strength of Catalysts E and F subsequent to their recorded useabove were respectively 20 and 16 pounds.

EXAMPLE III 1800 grams of commercially available activated carbonpellets measuring Ms inch in diameter having an ash content of 3.51percent were mixed with 5 liters of a solution prepared by mixing 3volumes of concentrated hydrochloric acid with 7 volumes of Water. Afterdigesting the material for 2 days at F. the solution was filtered fromthe activated carbon and the solids thoroughly washed until the washwater was free of chloride ion. The ash content of the dried acid washedcarbon was 1.37 weight percent which consisted predominantly of silicaalong with lesser amounts of iron, magnesium, calcium and titanium.

To the dried activated carbon, there was added 25.7 grams of palladiumchloride in 200 cc. of concentrated ammonium hydroxide along with 140cc. of water and 1000 cc. of methyl alcohol. After thoroughly agitatingthe mixture, the recovered solids were dried at 140 F. in a stream ofnitrogen. A sample of the catalyst was subsequently heat treated at 700F. in a stream of nitrogen for 4 hours at atmospheric pressure. Thecatalytic material possessed a palladium content of 1.08 weight percentand had a crush strength of 20 pounds.

A C -C feedstock as in Example I was introduced at the rate of 88 cc.per hour into a reactor containing 41 grams of the catalyst maintainedat a temperature of 210 220 F. and 600 p.s.i.g. of hydrogen. Productanalysis showed 4.4 milligrams of NH as primary amine per gram ofproduct and 0.0 milligrams of NH as secondary amine. Increasing thereactor temperature to 280-290 F. and the feed rate to 140 cc. per hourresulted in a product anal ysis of 5.3 milligrams of NH as primary amineand 0.2 milligrams of NH as secondary amine.

Another sample of the catalyst heat treated at 700 F. under nitrogen wasfurther heat treated at 950 F. for 2 hours in a stream of hydrogenflowing at the rate of 1-2 cubic feet per hour at 600 p.s.i.g. Theaforementioned C -C feedstock was introduced at the rate of 85 cc. perhour into a reactor containing 40 grams of the catalyst maintained at210-220 F. and 600 p.s.i.g. of hydrogen. Product analysis showed 5.0milligrams of NH as primary amine per gram of product and 0.1 milligramsof NH as secondary amine. Increasing the reaction temperature to 280290F. and the feed rate to 140 cc. per hour resulted in a product analysisof 6.7 milligrams of NH:

as primary amine and 0.2 milligrams of NH as secondary amine.

Another 400 gram sample of the catalyst heat treated at 700 F. undernitrogen was introduced to a reactor such that the bed depth was 10inches and the feedstock was introduced at a volume hourly spacevelocity of 0.50, hydrogen introduced at 10 cubic feet per hour,hydrogen pressure of 580 p.s.i.g. and a temperature of 300350 F. Thereaction was conducted over a period of 6 weeks and gave the followingresults. At the end of the first week, product analysis showed 9.4milligrams of NH as primary amine and 0.9 milligrams of NH as secondaryamine; second week 9.3 milligrams of NH as primary amine and 0.5milligrams of NH as secondary amine, third week 9.4 milligrams of NH asprimary amine and 0.4 milligrams of NH as secondary amine; sixth week8.9 milligrams of NH as primary amine and 0.4 milligrams of NH assecondary amine. As can be seen, the heat treatment provided thecatalyst with prolonged activity and selectivity toward converting thenitroparafiin to primary amine with minimal formation of secondaryamine. After six weeks of use as described above, the catalystsurprisingly possessed an increased crush strength of 22.7 pounds andhad a high selectivity toward secondary alkyl primary amines in that 92%of the nitroparaflin converted formed primary amine.

EXAMPLE IV Another catalyst was prepared as described in Example III andwas analyzed to contain 0.97 weight percent palladium on an activatedcarbon having 1.84% ash content other than palladium and a surface areaof 1,288 square meters per gram. 337 grams of this catalyst which hadbeen heat treated with nitrogen at 700 F. was placed in a hydrogenationreactor and a C C n-paraffin feedstock as in Example I was introduced ata feed rate of 1.1 volume of liquid feed per volume of catalyst per hourunder a hydrogen pressure of 600 p.s.i.g. with a flow of hydrogen of 10cubic feet per hour. The catalysts initial crush strength was measuredat 18 pounds and after being employed for a period of 804 hours wasdetermined to have a crush strength of 19.7 pounds. From the datasummarized below, it will be seen that the catalyst remained active overthe 804 hour period of operation with the primary amine productionremaining constant, the secondary amine formation decreasing which infact resulted in a higher selectivity towards primary amine.

Primary Secondary amine amine After 804 hours of operation, introductionof the nitroparafiin feedstock was interrupted and the catalyst washeated in situ within the reactor in a stream of hydrogen flowing at therate of 10 cubic feet per hour at 600 p.s.i.g. and 900 F. for a periodof 4 hours. This treatment served to regenerate the catalyst by removingdeposits thereon. The regenerated catalyst was thereafter contacted withthe feedstock under the conditions described above and from the datasummarized below it will be seen that the regenerated catalyst was notonly more active after regeneration but also possessed superiorselectivity in that increased production of primary amine and lesssecondary amine resulted after a comparable time on stream. The

a r ported in the tables represents milligrams of NH and NH as primaryamine and secondary amine per gram of product.

Primary Secondary Two catalysts composed of respectively 1% palladium onactivated carbon and 1% platinum on activated carbon were heat treatedto 900 F. in a stream of 2 cubic feet per hour of hydrogen for 3 hoursat 600 p.s.i.g. 20 gram samples (50 cc.) of each catalyst was charged toa hydrogenation reactor and a feedstock containing 16 weight percent C-C nitroparaffin in a C -C n-paraffin was introduced at the rate of 30cc. per hour into the reactor along with 1.8 cubic feet of hydrogen perhour at conversion conditions of 600 p.s.i.g. of hydrogen and an inletreactor temperature of 300 F. The conversion was permitted to proceedover a period of 24 hours. Analysis of the products from each reactordemonstrated the higher selectivity of the palladium catalyst toward theformation of secondary alkyl primary amines in that this catalystprovided 8.3 milligrams of NH as primary amine per gram of productwhereas the platinum catalyst produced 4.8 milligrams of NH as primaryamine. Moreover, the platinum catalyst produced twice the amount ofsecondary amine product as compared to the palladium catalyst. In termsof total equivalence expressed as primary amine, the palladium catalystwas more active in that it produced 11.1 milligrams of NH as primaryamine as compared to 10.4 milligrams of NH as primary amine produced bythe platinum catalyst.

EXAMPLE VI A 2% rhenium on activated carbon catalyst was prepared byimpregnating the carbon with perrhenic acid dissolved in dilute ammoniumhydroxide and subsequently drying at 220 F. for four hours in a nitrogenatmosphere. As in Example V, the catalyst was heat treated to 900 F. ina stream of 2 cubic feet per hour of hydrogen for 3 hours at 600p.s.i.g. The catalyst, 20 grams (50 cc.), was charged to a hydrogenationreactor and contacted with the feedstock and conditions recited inExample V for 24 hours. Analysis of the product demonstrated the higherselectivity of the rhenium catalyst toward the formation of secondaryalkyl secondary amines in that this catalyst provided 4.1 milligrams ofNH as secondary amine and 3.4 milligrams of NH as primary amine. Interms of total equivalence expressed as milligrams of NH as primaryamine, the rhenium catalyst was most active in that it produced 11. 6milligrams of NH as primary amine.

EXAMPLE VII Other catalyst evaluations were conducted whereinhydrogenation of a C -C nitroparafiin feedstock as described in ExampleI was contacted with a commercially available inch pelleted nickel onkieselguhr catalyst at temperatures ranging from 360 to F. Solubilizednickel was detected in the reactor efiiuent in significant amounts atreaction temperatures below 300 F. and the elution of nickel increasedrapidly as the tem perature of the reaction was lowered progressively to195 F. Illustratively, at the following reaction temperatures therespective concentrations of nickel in p.p.m. were detected in theproduct: 360 F.less than 1, 325 F.1, 300 F.-1, 200 F.14 and 195 F.-31.

In another evaluation 755 grams (620 cc.) of nickel on kieselguhrcatalyst was contacted at temperatures ranging from 315 to 385 F. with afeed composed of C C nitroparaffin as in Example I at the feed rate ofPrimary Secondary amine amine As can be seen under conditions favorablefor little or no solubilization of nickel in the amine product, theactivity of the catalyst was steadily reduced.

Another noble metal catalyst consisting of 0.6 weight percent platinumon eta-alumina having a crush strength of 16 pounds was employed in thehydrogenation of a C -C nitroparafiin feedstock as in Example I whichwas introduced at the rate of 94 cc. per hour at reaction conditions of225 F., 600 p.s.i.g. of hydrogen pressure and a liquid hourly spacevelocity of 1.0. After 108 hours on stream, the crush strength of thecatalyst was 3 pounds.

I claim:

1. In the low temperature hydrogenation of nitrated hydrocarbons to formcorresponding amines having from 6 to 25 carbon atoms along withby-product water wherein said hydrocarbon and hydrogen are contactedwith a catalyst composed of a group VIIB or VIII metal on carbon underhydrogenation conditions including reac tion temperatures of from 100 to450 F., the improvement which comprises carrying out said hydrogenationin the presence of said catalyst stabilized by heating said catalyst forat least one hour at a temperature of between 500 and 1200 F. in thepresence of a non-oxidizing gas selected from the group consisting ofnitrogen, mehtane, argon, helium, neon, ethane, propane, hydrogen andmixtures of hydrogen and light paraflins under a pressure of to 1,000p.s.i.g.

2. The process according to Claim 1 wherein said stabilized catalyst isregenerated by contacting with said non-oxidizing gas at a temperatureof from 500 to 1200 F.

3. The process according to Claim 1 where said pres sure is 300 to 700p.s.i.g.

4. The process of Claim 1 wherein said non-oxidizing gas is hydrogen.

5. The process of Claim 1 wherein said non-oxidizing gas is nitrogen.

6. The process of Claim 1 wherein said temperature is from 700 to 1100F.

7. The process of Claim 1 wherein said catalyst is heated for a periodof 2 to 8 hours.

8. The process of Claim 1 wherein said non-oxidizing gas is introducedto said catalyst at the rate of at least standard cubic feet per hourper square foot of reactor cross section over a period of at least 2hours.

9. The process of Claim 1 wherein said carbon has an ash content ofbelow 5.0 weight percent.

10. The process of Claim 1 wherein said carbon has an ash content ofbelow 2.0 weight percent.

11. The process of Claim 1 wherein said Group VIIB metal is rhenium.

12. The process of Claim 1 wherein said Group VIII metal is selectedfrom the group platinum, palladium, rhodium or ruthenium.

References Cited UNITED STATES PATENTS 3,053,898 9/1962 Heath et al252447 3,641,121 2/1972 Swift 252447 3,409,703 11/1968 Engelbrecht eta1. 252447 3,144,496 8/1964 Rylander et al. 260583 M 3,696,153 10/1972Kershaw et al. 260-583 K 3,194,839 7/1965 Robinson et a1. 2524473,271,473 9/1966 Engelbrecht et al. 252447 3,328,465 6/1967 Spiegler252432 2,823,235 2/1958 Penrose et al 260-583 M 3,255,248 6/ 1966Suessenguth et al. 260583 M 3,594,419 7/1971 Rosenthal 260-583 M3,470,250 9/1969 Patterson et a1. 260583 M OTHER REFERENCES J. Org.Chem., Breitner, December 1959, pp. 1855'- 1857.

LEWIS GOTTS, Primary Examiner D. R. Phillips, Assistant Examiner

1. IN THE LOW TEMPERATURE HYDROGENATION OF NITRATED HYDROCARBONS TO FORMCORRESPONDING AMINES HAVING FROM 6 TO 25 CARBON ATOMS ALONG WITHBY-PRODUCT WATER WHEREIN SAID HYDROCARBON AND HYDROGEN ARE CONTACTEDWITH A CATALYST COMPOSED OF A GROUP VIIB OR VIII METAL ON CARBON UNDERHYDROGENATION CONDITIONS INCLUDING RECTION TEMPERATURES OF FROM 100 TO450*F., THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID HYDROGENATIONIN THE PRESENCE OF SAID CATALYST STABILIZED BY HEATING SAID CATALYST FORAT LEAST ONE HOUR AT A TEMPERATURE OF BETWEEN 500 AND 1200*F. IN THEPRESENCE OF A NON-OXIDIZING GAS SELECTED FROM THE GROUP CONSISTING OFNITROGEN, MEHTANE, ARGON, HELIUM, NEON, ETHANE, PROPANE, HYDROGEN ANDMIXTURES OF HYDROGEN AND LIGHT PARAFFINS UNDER A PRESSURE OF 0 TO 1,000P.S.I.G.